Question

An ion $M^{+2}$ forms the complexes as
${\left[M{\left(H_{2}O\right)}_6\right]}^{2+}$ ${\left[M{\left(en\right)}_3\right]}^{2+}$ ${\left[MB{r}_6\right]}^{4-}$
Match the complex with the appropriate colour respectively.

• A. Green, blue & red
• B. Blue, red & green
• C. Green, red & blue
• D. Red, blue & green

Answer 1

The correct option is A Green, blue & red

Order of stability of complex:

$\left[M\right(en{)}_3{]}^{2+}>\left[M\right(H_{2}O{)}_6{]}^{2+}>[MB{r}_6{]}^{4-}$

Intensity of colour $\propto \frac{1}{Energygap}$

Since order of ligand field strength is $en>H_{2}O>Br$

$\therefore$ energy gap order is $\left[M\right(e{n}_3{]}^{2+}<\left[M\right(H_{2}O{)}_6{]}^{2+}<[MB{r}_6{]}^{4-}$ since red is more intense

$\therefore \left[M\right(en{)}_3{]}^{2+}$ is Red colour and $\left[M\right(H_{2}O{)}_6{]}^{2+}$ is green colour and $[MB{r}_6{]}^{4-}$ is blue in colour.